Previously these wind energy generators were constructed and regulated in ways such as that presented in S. Müller, M. Deicke, Rik W. de Doncker: “Doubly fed induction generator systems for wind turbines—a viable alternative to adjust speed over a wide range at minimal cost”, IEEE industry application magazine, May/June 2002. The converter is currently preferably designed as a back-to-back circuit of two self-commutated indirect converters. Each converter is assigned a regulation unit. The corresponding regulation unit determines the switching states of the assigned converter to be implemented and communicates these switching states to the control circuits of the converter. The control circuits are generally integrated into the converter.
The rotor winding-side converter determines with its switching states the currents flowing in the rotor windings. The network-side converter must regulate the direct current to a constant value. The network-side converter can also regulate the direct current for a number of windmills. In this case a direct current network is arranged between a number of windmills. In each case however the rotor winding-side converter is assigned to precisely one windmill.